Magnetic head with a conductive underlayer above substrate

ABSTRACT

A magnetic head includes a wafer substrate and a conductive underlayer formed directly on the substrate. An insulating layer is formed above the conductive layer. A reader and/or writer thereof is formed above the insulating layer. Another magnetic head includes a substrate and an insulating underlayer formed above the substrate. A conductive underlayer is formed above the insulating underlayer. An insulating layer is formed above the conductive underlayer. At least one device is formed above the insulating layer, the at least one device being selected from a group consisting of readers, writers, and combinations thereof. Tape drive systems and methods for forming such heads are also presented.

FIELD OF THE INVENTION

The present invention relates to magnetic head structures, and moreparticularly, this invention relates to a magnetic head structure havinga conductive underlayer deposited between the wafer and the nearestshield.

BACKGROUND OF THE INVENTION

Business, science and entertainment applications depend upon computersto process and record data. In these applications, large volumes of dataare often stored or transferred to nonvolatile storage media. Thisstorage media may include magnetic discs, magnetic tape cartridges,optical disk cartridges, floppy diskettes, or floptical diskettes.Typically, magnetic tape is the most economical and convenient means ofstoring or archiving the data. Storage technology is continually pushedto increase storage capacity and storage reliability. Improvement indata storage densities in magnetic storage media, for example, hasresulted from improved medium materials, improved error correctiontechniques, and decreased areal bit sizes. The data capacity ofhalf-inch magnetic tape, for example, is currently measured in hundredof gigabytes on 512 or more data tracks.

The improvement in magnetic medium data storage capacity arises in partfrom improvements in the magnetic head assembly used for reading andwriting data on the magnetic storage medium. A major improvement intransducer technology arrived with the magnetoresistive (MR) sensororiginally developed by the IBM Corporation. The MR sensor transducesmagnetic field changes in an MR stripe to resistance changes, which areprocessed to provide digital signals. Data storage density can beincreased because a MR sensor offers signal levels higher than thoseavailable from conventional inductive read heads for a given read trackwidth. Moreover, the MR sensor output signal depends only on theinstantaneous magnetic field intensity in the storage medium and isindependent of the magnetic field time-rate-of-change arising fromrelative sensor/medium velocity.

The quality of data stored on a magnetic tape may be increased byincreasing the number of data tracks on the tape, which also decreasesthe distance between adjacent tracks and forces neighboring read/writeheads closer together. More tracks are made possible by reducing featuresizes of the read and write elements, such as by using thin-filmfabrication techniques and MR sensors. In operation the magnetic storagemedium, such as tape or a magnetic disk surface, is passed over themagnetic read/write (R/W) head assembly for reading data therefrom andwriting data thereto. In modern magnetic tape recorders adapted forcomputer data storage, read-while-write capacity with MR sensors is anessential feature for providing fully recoverable magnetically storeddata. The interleaved R/W magnetic tape head with MR sensors allowsincreased track density on the tape medium while providingbi-directional read-while-write operation of the tape medium to giveimmediate read back verification of data just written onto the tapemedium. A read-while-write head assembly includes, for each of one ormore data tracks, a write element in-line with a read element, hereindenominated a R/W track pair, wherein the gap of the read element isaligned with the gap of the write element, with the read elementpositioned downstream of the write element in the direction of mediummotion. By continually reading just-recorded data, the quality of therecorded data is immediately verified while the original data is stillavailable in temporary storage in the recording system. In theinterleaved head, the R/W track-pairs are interleaved to form two-rowsof alternating read and write elements. Alternate columns (track-pairs)are thereby disposed to read-after-write in alternate directions of tapemedium motion. Tape heads suitable for reading and writing onhigh-density tapes require precise alignment of the track-pair elementsin the head assembly.

FIG. 1 illustrates a head 100 which can also function as aread-while-write head. As shown, the head includes several R/Wtransducer pairs 102 in a “piggyback” configuration. Servo readers 104are positioned on the outside of the array of R/W transducer pairs 102.The servo readers 104 follow servo tracks for the particular data “band”of the tape being read or written to. Thus, signals from the servoreaders are used to keep the head aligned with the band. The tape mayhave a single data band, or many data bands, and each band may have oneor more servo tracks.

When the head is constructed, layers are formed on a substrate 110 ingenerally the following order for the R/W transducer pairs 102: anelectrically insulative layer 112, a first shield (S1) 114 formeddirectly on the insulative layer 112, a sensor 116 also known as a readtransducer, a second shield (S2) 118, and first and second writer poletips (P1, P2) 120, 122. Note also that the second shield 118 and firstwriter pole tip 120 may be merged into a single structure.

Tape heads are constantly contacting the tape media during reading,writing and locating. This continuous contact can degrade headperformance, resulting in an increase in error rates. Degradation can becaused by a variety of mechanisms. One is head wear caused by motion ofthe magnetic recording tape. Repeated passes of the tape medium over thetape head surface may eventually wear away some of the surface, whichcan impair head performance. This can be a particular problem forthin-film magnetic heads where the thin-film layer structure is lesswear resistant than the tape supporting head portions, possibly leadingto an unacceptably short lifetime for the magnetic head assembly. Veryhard wear-resistant layers such as diamond-like carbon ortitanium-carbide on the air bearing surfaces of magnetic heads inhibitgap erosion. However, such layers must be very thin, being perhaps 20nanometers thick to ensure close head-tape spacing. Because they must beso thin, they tend to wear off over time.

Another magnetic head performance degradation problem is due to pittingand clogging of the insulation layer positioned between the substrateand nearest shield. It is believed that charging of the tape runningover the head coupled with biasing of the shields and/or substrate cancreate high electric fields between head and tape and in the insulatinglayer, and cause electrostatic attraction of debris and even breakdown.This in turn tends to fracture or otherwise damage the insulating layer,forming pits therein. The pits become regions for debris accumulation,which in turn causes a variety of problems including shorting across theinsulating layer and lifting of the tape away from the transducers.Also, the irregular electric field distribution in the preferred wafersubstrate material Al₂O₃—TiC, or “AlTiC”, has hot spots at TiC graincorners. One solution to this problem has been contemplated. Heads maybe made out of alternative ceramic wafers. However, other wafermaterials are found to be less desirable due to generally poorer wear,fabrication issues, and heat conduction characteristics.

Another idea has been to make the undercoat thicker to reduce thefields. However, this resulted in more pronounced, wear. A thinnerundercoat would seem desirable, but is found to have little benefit dueto high fields and faster clogging.

There is accordingly a clearly-felt need in the art for a read/writehead assembly with improved reliability. These unresolved problems anddeficiencies are clearly felt in the art and are solved by thisinvention in the manner described below.

SUMMARY OF THE INVENTION

A magnetic head according to one embodiment of the present inventionincludes a wafer substrate and a conductive underlayer formed on thesubstrate. An insulating layer is formed above the conductive layer. Atleast one device is formed above the insulating layer. The at least onedevice is selected from a group consisting of readers, writers, andcombinations thereof. In a preferred embodiment, the conductiveunderlayer is formed directly on the substrate.

A magnetic head according to another embodiment of the present inventionincludes a substrate and an insulating underlayer formed above thesubstrate. A conductive underlayer is formed above the insulatingunderlayer. An insulating layer is formed above the conductiveunderlayer. At least one device is formed above the insulating layer.The at least one device is selected from a group consisting of readers,writers, and combinations thereof.

A magnetic head according to another embodiment of the present inventionincludes a wafer substrate. At least one device is formed above thewafer substrate. The at least one device is selected from a groupconsisting of readers, writers, and combinations thereof. A closure isformed. A conductive underlayer is formed between one or more of the atleast one devices and the closure.

A tape drive system includes a head as recited above, a drive mechanismfor passing a magnetic recording tape over the head, and a controller incommunication with the head.

Methods for forming such heads are also presented.

Other aspects and advantages of the present invention will becomeapparent from the following detailed description, which when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings.

FIG. 1 is a representative view of a typical prior art multitrack tapehead having a multitude of readers and writers.

FIG. 2 is a representative view of a multitrack tape head according toone embodiment.

FIG. 3 is a flow diagram depicting a process for forming the head ofFIG. 2.

FIG. 4 is a circuit diagram for biasing a shield according to oneembodiment.

FIG. 5 is a representative view of a multitrack tape head according toone embodiment.

FIG. 6 is a representative view of a multitrack tape head according toone embodiment.

FIG. 7 is a representative view of a multitrack tape head according toone embodiment.

FIG. 8 is a representative view of a multitrack tape head according toone embodiment.

FIG. 9 is a schematic diagram of the tape drive system.

BEST MODE FOR CARRYING OUT THE INVENTION

The following description is the best embodiment presently contemplatedfor carrying out the present invention. This description is made for thepurpose of illustrating the general principles of the present inventionand is not meant to limit the inventive concepts claimed herein.Further, particular features described herein can be used in combinationwith other described features in each of the various possiblecombinations and permutations.

In the drawings, like and equivalent elements are numbered the samethroughout the various figures.

As described herein, preferred embodiments of the invention includes amagnetic recording head having a conducting thin film layer, hereinreferred to as a “conductive underlayer”, deposited directly on thewafer, before the first magnetic shield insulator. In other embodiments,a thin insulating underlayer is formed between the conductive underlayerand the substrate.

The preferred wafer material for magnetic recording heads is commonlyknow as AlTiC, which is a ceramic composite material consisting of a seaof insulative aluminum oxide (alumina, Al₂O₃) plus an irregular butinterconnected network of conductive titanium carbide (TiC). The unevendistribution of TiC creates an irregular electric field that extendsinto the tape region and into the undercoat insulation. Tis can promoteelectrical discharges into the insulator in areas where the field ishigh, e.g., at edges of TiC grains. The discharges have been found toproduce pits in any overlay insulation and may play a role in othertape-head material transfer processes. The conductive underlayer in theheads described herein eliminates the electrified “hot spots” and thusprovides a uniform electric field at the interface with the sensor lowershield. Another benefit of the conductive underlayer is that itdistributes heat and thus can assist in cooling the sensors duringoperation.

FIG. 2 illustrates a tape head 200 according to an illustrativeembodiment of the invention. As shown, a conductive underlayer 202 isformed on a substrate 204 of AlTiC. In a preferred embodiment, theconductive underlayer 202 is formed directly on the substrate 204. Tapeheads have 8, 16, 24, or more sets of readers and/or writers per head,and generally the shields of the various R/W pairs 208 must be isolatedfrom one another. Accordingly, an insulating layer 206, e.g., ofaluminum oxide, is formed between the lower shields 210 and theconductive underlayer 202.

R/W pairs 208 and servo readers 209 are formed above the insulatinglayer 206. Each R/W pair includes a reader and a writer. The readerincludes a first shield (S1) 210, a sensor 212 also known as a readelement or MR element, and a second shield (S2) 214. The writer includesfirst and second writer pole tips (P1, P2) 216,218. Note also that thesecond shield 214 and first writer pole tip 216 may be merged into asingle structure. Also note that additional layers such as insulationbetween the shields and/or pole tips and surrounding the sensor, as wellas composition and constructions of the R/W pair components, are wellknown and so description thereof has been omitted.

FIG. 3 illustrates a method 300 to implement an embodiment of theinvention. In step 302 of the method 300, the conductive underlayer isdeposited above, and preferably directly on, the wafer at one of thefirst steps in processing. Any suitable process for depositing theconductive underlayer may be implemented, including sputtering, plating(may require conductive seed layer), etc. The deposition step 302 may befollowed by deposition of a thin insulating layer above, and preferablyon, the conductive underlayer in step 304. A planarization step 306 isperformed on the insulating layer, which in turn enables fabricating themagnetic sensors on the insulating layer. In step 308, the variousreader and/or writer components are formed above the insulating layer.Note that additional layers may be added without straying from the scopeof the invention.

To understand what the conductive underlayer 202 does, one mustunderstand the composition of the substrate 204. For purposes ofillustration, a substrate 204 of AlTiC will be described. Note that thesame principles apply to other current and future substrates having acomposition of conductive and nonconductive grains.

AlTiC has been used extensively in the recording industry because itexhibits excellent thermal and mechanical properties and strikes a goodbalance between these properties and machinability.

AlTiC is not a uniform material, rather it is a mixture of aluminumoxide powder and TiC grains. The mixture is blended, then compressedunder heat and pressure to form a coupon. The finished coupon has goodthermal conductivity and very high electrical conductivity. A typicalcomposition is 25-35 wt % or more of TiC grains randomly dispersed inthe coupon material.

The coupon is then cut into wafers, and wafer surfaces are polished sothat each wafer can be used as a substrate 204. The polished wafersurface has regions of exposed aluminum oxide, and regions of exposedTiC. The TiC is electrically conductive (almost as conductive as somemetals), while the aluminum oxide is electrically insulative.

When an electrical contact is placed on the substrate 204 and thenconnected to a power supply, the conductive regions come to thatpotential set by the power supply. Particularly, the TiC portions areset, for instance, at 1.5 V relative to ground. Then, electric fieldsemanate from the grains of TiC. These electric fields have largegradients, as the grains are irregular. Computer modeling performed atthe direction of the inventor has shown large electric fields emanatingfrom the grains.

As mentioned above, because AlTiC is electrically conductive, a layer ofaluminum oxide is typically placed on the AlTiC substrate 204 to isolateit from the readers and writers. However, excessive electric fields areassociated with pitting in the aluminum oxide of the prior artinsulating layer. See FIG. 1.

By placing a conductive underlayer 202 directly on the substrate 204,the conductive underlayer 202 will have the same potential as thesubstrate 204. Now, the electric field emanating from the conductiveunderlayer 202 and into the insulating layer 206 is reduced in magnitudeand uniform. Modeling has shown that the field emanating from the grainsof TiC can be 5 times higher (or more) than the fields emanating fromthe conductive underlayer 202. The diminished and uniform fieldemanating from the conductive underlayer 202 reduces the pitting of theoverlying insulating layer 206 and debris accumulation.

The conductive underlayer 202 can be formed from any conductivematerial, though good electrical conductors are preferred, i.e.,materials with low electrical resistivity. Metals are particularlypreferred due to their high electrical conductivity and high thermalconductivity. Illustrative wear resistant metals include Sendust(Al—Si—Fe), NiFe, Ta, etc. Additional conductive materials includeconductive ceramics. The conducting underlayer can be magnetic ornonmagnetic. Applying the conducting underlayer enables the designer andmanufacturer to use conventional disk and tape head wafer material.

While not foreclosing the following metals from within the scope of theinvention, it is believed that the following metals are less desirablechoices than other metals described above. Copper may not be a goodchoice as it may exhibit interactive effects with a tape passingthereacross. Gold may not be a good choice as it may tend to smear dueto tape friction.

The conductive underlayer 202 is preferably a few tenths of a micrometer(μm) thick or more, as measured perpendicular to the deposition plane.An illustrative thickness range is about 0.01 μm to about 1 μm thick,though thicker and thinner dimensions can be selected per the desires ofthe designer. This thickness range has been found to provide thebenefits listed herein.

In many situations, it may be desirable to clamp the potential of theshields 210, 214. FIG 4 depicts an illustrative circuit diagram of abiasing circuit 400 of the MR element 212 and associated shield(s)(lower shield 210 shown, circuit 400 may be coupled to the upper shield214 (FIG. 2) or both shields 210, 214) according to one embodiment. Asshown in FIG. 4, the leads 406, 407 of the MR element 212 are connectedto a current source 408 and a ground 410. Reference resistors 412, 414are present, and are preferably equal to provide common mode rejectionof noise picked up by the leads. Illustrative resistance values for thereference resistors are 150Ω each. Additional resistors 416, 418,typically of about 50KΩ are positioned on a node 420 coupled to theshield 210. This configuration sets the voltage of the shield 210 atabout the average of the two leads 406, 407.

In the embodiment shown in FIG. 4, if the reference voltage is 3.0V,then the voltage on the node coupled to the shield 210 is about 1.5V.Note that these values for voltages and resistance, and indeed thisparticular circuit diagram, are provided by way of example only, and onepracticing the invention is free to select any desired configuration.

The inventor has observed that under certain conditions and with somemedia, debris can accumulate across the insulating layer 206, creating aconductive path between the lower shield 210 and the conductiveunderlayer 202. If this happens and the resulting resistance iscomparable to the two resistors 416, 418, then the bias current maybecome diverted and the MR output degraded. This effect is minimizedwhen the conductive underlayer and shields 210 are at the samepotential. Thus, in the previous example, because the shield(s) arebiased at 1.5V, it is desirable to also set the potential of theconductive underlayer 202 at 1.5V. In embodiments where the conductiveunderlayer 202 is positioned directly on the substrate 204, this may beaccomplished by biasing the conductive underlayer 202 and/or substrate204 to 1.5V.

However, it is also desirable that the substrate 204 have low AC and DCimpedance to ground so that the substrate 204 can act as an electricalshield. Thus, for electromagnetic interference (EMI) shielding, it maybe desirable to connect the substrate 204 directly to ground, to groundthrough a resistor, or to otherwise have a lower potential than theshields. In addition, the substrate and associated circuits may be ACcoupled to ground via coupling capacitors.

An optional thin insulating underlayer 500 can be formed between thesubstrate 204 and the conductive underlayer 202, as shown in FIG. 5.Because the conductive underlayer 202 is now isolated from the substrate204, the designer can set the potential of the conductive underlayer 202to a value different than that of the substrate 204. If the potential ofthe conductive underlayer 202 is set to the potential of the shields210, 214, any occurrence of debris-induced shorting between the lowershield 210 and the conductive underlayer 202 will be of little or noconsequence (keeping in mind that it is desirable to isolate the shields210, 214 in one R/W pair from the shields 210, 214 of the other R/Wpairs).

A preferred thickness of the insulating underlayer 500 would be lessthan about 5 μm and preferably less than about 0.25 μm, e.g., 0.2 μm,0.1 μm, etc. as measured perpendicular to its plane of deposition. Verythin dimensions of the insulating underlayer 500 (when present) maximizethe benefits of the conductive underlayer 202 as described herein.Particularly, the fields emanating from the conductive grains in thesubstrate 204 are present between the conductive underlayer 202 andsubstrate 204, and are substantially contained by the conductiveunderlayer 202.

While any conventional insulating material can be used to form theinsulating underlayer, a preferred material for the insulatingunderlayer 500 is aluminum oxide. In such embodiments, the aluminumoxide layer is preferably a very hard aluminum oxide formed by slowdeposition such that it is thin, yet resists the aforementioned pitting.Ideally, the aluminum oxide is sapphire-like, and can be similar to orthe same as the aluminum oxide used to insulate the read elements in thehead.

The think insulating underlayer 500 also serves as a sacrificial layerfor debris accumulation. It is well known that debris from the tapetends to accumulate and even embed in the head. If debris accumulationoccurs, it is preferable that it occur in the gap between the substrate204 and the conductive underlayer 202 rather than between the conductiveunderlayer 202 and the shield 210.

The conductive underlayer 202 of FIG. 5, as well as the otherembodiments of the present invention, can be biased by adding a source510 of alternating or direct current. This allows the voltage of theconductive underlayer 202, for example, to be matched to that of thesubstrate 204. In a further variation, as depicted in FIG. 6, theconductive underlayer 202 can be electrically coupled to the substrate204. This also allows voltage matching between the conductive underlayer202 and the substrate 204.

The embodiment of FIG. 5 may be performed by varying the process of FIG.3. Particularly, instead of forming the conductive underlayer 202 on thesubstrate 204 in step 302, the insulating underlayer 500 is formed onthe substrate 204, then the conductive underlayer 202 is formed abovethe insulating underlayer 500.

It should be kept in mind that additional layers may be added from anyof the embodiments described herein in each of the possible permutationsand variants of the present invention. For example, FIG. 6 depicts avariation of the embodiment shown in FIG. 5, where a second conductiveunderlayer 602 is positioned between the substrate 204 and the lowerinsulating layer 500.

FIG. 7 illustrates yet another embodiment of the head 200 where aconductive underlayer 702 is positioned between a closure 704 and theR/W pairs 208. Because closures are typically constructed of AlTiC andother such materials, the benefits afforded by the closure-sideconductive underlayer 702 may be similar to those afforded bysubstrate-side conductive underlayer 202.

The conductive underlayer(s) in the various embodiments may also bepatterned to some desired shape. In one example, shown in FIG. 8, theconductive underlayer 202 is patterned to be located in proximity to theservo readers 209 and/or the array of R/W pairs 208. In another example,not shown, the conductive underlayer can be patterned to be located inproximity to the servo readers and/or each individual R/W pair. Isolatedsegments of the conductive underlayer further reduce the chance ofshorting between the substrate and lower shields.

Any of the above embodiments or combinations of portions thereof canalso be applied to any type of magnetic heads and magnetic recordingsystems, both known and yet to be invented. For example, the teachingsherein are easily adaptable to interleaved heads.

FIG. 9 illustrates a simplified tape drive which may be employed in thecontext of the present invention. While one specific implementation of atape drive is shown in FIG. 9, it should be noted that the embodimentsof the previous figures may be implemented in the context of other typesof magnetic-based systems.

As shown, a tape supply cartridge 920 and a take-up reel 921 areprovided to support a tape 922. These may form part of a removablecassette and are not necessarily part of the system. Guides 925 guidethe tape 922 across a preferably bidirectional tape head 926, of thetype disclosed herein. Such tape head 926 is in turn coupled to acontroller assembly 928 via an I/O cable 930. The controller 928, inturn, controls head functions such as servo following, write bursts,read functions, etc.

A tape drive, such as that illustrated in FIG. 9, includes drivemotor(s) to drive the tape supply cartridge 920 and the take-up reel 921to move the tape 922 linearly over the head 926. The tape drive alsoincludes a read/write channel to transmit data to the head 926 to berecorded on the tape 922 and to receive data read by the head 926 fromthe tape 922. An interface is also provided for communication betweenthe tape drive and a host (integral or external) to send and receive thedata and for controlling the operation of the tape drive andcommunicating the status of the tape drive to the host, all as will beunderstood by those of skill in the art.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

1. A magnetic head, comprising: a plurality of transducing devices forreading and/or writing to a media; a wafer substrate; a conductiveunderlayer formed on the substrate and interposed between thetransducing devices and the substrate; an insulating layer formed abovethe conductive underlayer and interposed between the transducing devicesand the conductive underlayer; and the plurality of transducing devicesbeing formed above the insulating layer and being selected from a groupconsisting of readers, writers, and combinations thereof, wherein eachof the readers includes shield layers formed above the insulating layerand positioned on opposite sides of a sensor of the reader.
 2. The headas recited in claim 1, wherein the substrate is a composite materialcomprising a mixture of electrically conductive and nonconductivematerials.
 3. The head as recited in claim 1, wherein the conductiveunderlayer is formed directly on the substrate.
 4. The head as recitedin claim 3, wherein the conductive underlayer is formed of a metal. 5.The head as recited in claim 4, wherein the metal is selected from agroup consisting of Sendust, NiFe, Ta, and combinations thereof.
 6. Thehead as recited in claim 1, wherein the plurality of transducing devicesincludes at least three devices formed above the insulating layer, theconductive underlayer being a single contiguous layer extending underthe at least three devices.
 7. The head as recited in claim 1, whereinthe devices are an array of piggybacked read/write pairs.
 8. The head asrecited in claim 1, further comprising a closure, and a secondconductive underlayer positioned between the closure and one or more ofthe transducing devices.
 9. The head as recited in claim 1, wherein theconductive underlayer is patterned.
 10. The head as recited in claim 1,wherein the conductive underlayer has a thickness of between about 0.1μm to about 1 μm thick as measured perpendicular to a plane ofdeposition thereof.
 11. A tape drive system, comprising: a head asrecited in claim 1; a drive mechanism for passing a magnetic recordingtape over the head; and a controller in communication with the head. 12.A magnetic head, comprising: a plurality of transducing devices forreading and/or writing to a media; a substrate; an insulating underlayerformed above the substrate and interposed between the transducingdevices and the substrate; a conductive underlayer formed above theinsulating underlayer and interposed between the transducing devices andthe insulating underlayer; a second insulating layer formed above theconductive underlayer and interposed between the transducing devices andthe conductive underlayer; the plurality of transducing devices beingformed above the second insulating layer and being selected from a groupconsisting of readers, writers, and combinations thereof; and at leasttwo shield layers formed above the second insulating layer andpositioned on opposite sides of a sensor of each reader to shield thatdevice.
 13. The head as recited in claim 12, wherein the plurality oftransducing devices includes readers having lower and upper shields,wherein the lower shield of each reader is positioned closer to thesecond insulating layer than the upper shield, wherein the lower shieldis biased at a potential greater than a potential of the substrate. 14.The head as recited in claim 13, wherein the conductive underlayer isbiased at a potential about equal to the potential of the lower shield.15. The head as recited in claim 12, wherein the insulating underlayeris sapphire-like aluminum oxide.
 16. The head as recited in claim 12,wherein the insulating underlayer has a thickness of less than about 1μm as measured perpendicular to a plane of deposition thereof.
 17. Thehead as recited in claim 12, wherein the plurality of transducingdevices is an array of the transducing devices, and wherein theconductive underlayer is a single contiguous layer extending under thearray of devices.
 18. The head as recited in claim 12, wherein theconductive underlayer has a thickness of between about 0.1 μm to about 1μm thick as measured perpendicular to a plane of deposition thereof. 19.A tape drive system, comprising: a head as recited in claim 12; a drivemechanism for passing a magnetic recording tape over the head; and acontroller in communication with the head.
 20. A magnetic head,comprising: a plurality of transducing devices for reading and/orwriting to a media; a substrate; an electrically conductive underlayerformed from a non-magnetic material above the substrate and wherein theelectrically conductive underlayer is a single contiguous layerinterposed between the transducing devices and the substrate; and aninsulating layer formed above the electrically conductive underlayer andinterposed between the transducing devices and the electricallyconductive underlayer; wherein the plurality of transducing devices areformed above the insulating layer, the transducing devices beingselected from a group consisting of readers, writers, and combinationsthereof.